1. Field of the Invention
The invention relates to processing of channel-based and object-based sound in theaters, auditoriums and other viewing rooms that comply with DCI (Digital Cinema Initiatives), FIPS (Federal Information Processing Standards) and other security standards.
2. Background of the Invention
Throughout motion picture history, the sound and the picture have been processed for exhibition in individual processing devices. In the very early days of 35 mm film, the soundtrack was read from the film, its frequency response adjusted to compensate for
In the very early days of 35 mm film, the soundtrack was read from the film; its frequency response adjusted to compensate for the non-linear frequency response used in recording and for imperfections in the film reader. In later years, a separate sound processor was added to adjust the frequency response (equalize) as required considering the acoustics of the room. As audio processing became more sophisticated, the audio processing unit also became more sophisticated by, among other things, overcoming time delays caused by the inherent time delay created by the audio processing equipment itself and the distance between the front and the rear of the theater.
With the advent of digital cinema, motion picture studios enhanced security by requiring that both the audio and the video be encrypted using a robust technology and that video and audio signals be forensically marked, also known as “watermarking.” For cinema applications, forensic marking is required by industry standards to include the date, time and place where the movie is being played. AES-128 (Advanced Encryption Standard—128 bit) encryption, which is also used for financial transactions, was selected to secure the audio and video content during transport and storage. Movies are encrypted by the studios before they are sent to the cinemas or elsewhere for distribution in order to prevent piracy and other unauthorized use.
As the images are getting more precise, the number of sound channels also is increasing. Movies progressed from a single channel audio (mono) to stereo sound in which speakers were located behind the left and right sides of the screen. Later, “surround channels” were added, adding speakers to the sides of the theater and behind the audience. These are known as “channel-based” audio systems, which employ a distinct audio channel for each speaker (or group of speakers) in the auditorium. With the addition of more audio channels, for a given movie, sound editors place the sound in separate audio channels to drive the sound through specified speakers.
“Object-based” sound was then added to movies. With object-based sound, sound editors locate an individual sound (an audio object) so that it may be heard coming from a specific location within the three dimensional space of a theater.
The individual sound objects are made up of the actual sound and metadata which comprises sound attributes, including, but not limited to, the intended location of a sound object within a theater. In the prior art, the sound objects for a particular movie, including their associated metadata, are packaged along with the video of that movie. In the prior art, at theaters equipped with the necessary sound processing equipment and speakers, the audio processor renders the object-based audio along with theater specific configuration data to map the sound objects into one or more audio channels at correct levels to provide the intended sounds at the proper locations within the given theater. The conversion of the sound objects to theater specific audio channels based on the object's intended location and theater speaker locations is referred to in the art as “rendering”.
Since the security of cinema content is extremely important in the movie industry to prevent piracy, the industry has required audio and video data either to be encrypted or forensically marked whenever the data is outside a secure integrated media block (IMB). In prior art channel-based implementations, the audio contents, including the related metadata, are encrypted while the sound is being stored on a server. During playback, the audio and video content is decrypted and forensically marked within the IMB and sent to the projector and sound system. Security is maintained since everything outside the media block is either encrypted or forensically marked.
With the advent of object-based audio, theaters must be able to play and forensically mark that object-based sound, as well. Some prior art methods utilize an IMB with the features shown in FIG. 1 and a non-standard enhanced audio processing unit (EAPU) that is specifically designed to decrypt, render and forensically mark the object-based audio. These EAPUs are costly and require a theater to replace their standard audio processing units (APU) because standard APUs cannot render the object based audio.
Because the rendering and forensic marking process takes place outside the media block, the EAPUs require a synchronization signal to synchronize the audio with the video image. In addition, the audio signals which are received from the server encrypted are decrypted within the EAPU.
The required decryption, object rendering, forensic marking, and synchronization add considerable complexity to the audio processing process. Further, using the systems in the prior art, movie audio has to be rendered in real time to ensure that the movie is secure especially because the security related functions are located in an external device instead of the secure media block. Thus, each time that the movie is viewed within the same theater, the object-based audio signals must be re-rendered to the audio channels and forensically marked.
Thus, it is desirable in the art to find a method and device to play movies with object-based sound that complies with industry required security measures and does not require that a theater replace its standard audio processor. It is also desirable in the art to provide a method of playing a movie that complies with industry required security measures that conserves processing power to minimize operating costs. It is further desirable in the art to find a method and device to play movies with object-based sound that complies with industry required security measures in which all decryption, encryption, object rendering and forensic marking may be done within a single secure IMB.